The present invention relates generally to the field of semiconductor device manufacturing and, more particularly, to the field of shaping semiconductor materials by chemical etching.
In the fabrication of integrated circuits, techniques for selectively shaping materials such as single crystal silicon, polycrystalline silicon films, dielectric films and metal layers have required the use of lithographic masking and chemical etches, milling and combinations thereof to shape the films and layers. As an example, semiconductor devices such as transistors and integrated circuits are commonly fabricated in silicon using a mask of silicon dioxide for the selective introduction of dopants. The practice is to open windows in the oxide layer by etching through defined holes in a photoresist mask. The photoresist operations for each diffusion require first applying the photoresist, exposing it through an optical mask, developing it, and removing it after the oxide etching is completed. Photoresist operations are a major factor in determining device yield and result in a relatively large part of fabrication costs. These masking, etching and milling techniques have in part restricted the formation of optimum structures and the reliability of integrated circuits. The resulting disadvantages have been limited device operation, lower circuit densities, lower yield and reliability, and higher processing costs.